Drugs, adjuvant and fluid used during anesthesia

Introduction

The practice of anesthesia is intimately related to the administration of drugs, and knowledge of these drugs' action and side effects is essential to safe practice. Fluid therapy including the crystalloids, colloids and blood is an important aspect of anesthetic care. Means of delivering anesthetic inhalation drugs using vaporizer in anesthesia machine with a different breathing system has been discussed in module 2 of session 2 and session 3. Setting routes for intravenous administration of drugs, infusion and transfusion will be discussed in this module.

Today, there is more than one drug for the same pharmacologic effects. The selection of a particular drug should be based on the known characteristics of the drugs with its interactions with other drugs and clinical condition of the patient. A particular drug's effect may vary widely between patients. Some variation is predicted for example we have to decrease the dose of anesthetics for hypovolemic patient, debilitated patient and patient with known cardiovascular problems. There are also unpredictable drug effects which may deteriorate the patient condition therefore, it is always advisable to titrate the drug against response in order to avoid inadvertent over dosage although you are administering the calculated amount of drugs. Drug dosage listed in this module or elsewhere is a rough guide because the actual dose depends on specific indication as well as clinical condition of the patient.

The first and second session of this module introduces about the anesthetic agents in the form of inhalation and intravenously administered drugs to initiate and maintain anesthesia for surgical procedure. The pharmacologic principles, dosage, advantages and disadvantages of each anesthetic agent are described. In the third session muscle relaxants, anticholinergics and anticholinestrase which the anesthetist are using on daily base for maximizing exposure of surgical field, reversing the effects of muscle relaxants and then antagonizing the unwanted effect of muscle relaxants using anticholinergics will be described.

The fourth and fifth session discuss an adjuncts used for correcting a preexisting problem as well as to administer under anesthesia if acute problem on the preexisting chronic problem occur or to use them when need arise to treat emergency problem. The sixth, seventh and eighth session explain the management of fluid including blood transfusion and procedures to prepare, assemble, perform and maintain intravenous infusion.

Inhalation anesthetics are substances that are brought into the body via the lungs and are distributed with the blood into the different tissues. The main target of inhalation anesthetics is the brain. Inhalation anesthetics act either by amplifying inhibitory function or decreasing excitatory transmission at the nerve endings in the brain. Currently used inhalation anesthetics include halothane, enflurane, isoflurane, sevoflurane, desflurane, and nitrous oxide. Older volatile anesthetics include ether, chloroform, and methoxyflurane. Halothane is widely used in Ethiopia. In this session you will learn to adopt knowledge on pharmacologic principles, the mechanism of action of inhaled anesthetics & the pharmacologic profile of specific inhaled anesthetics with their advantages and disadvantages as well as skill and right attitudes to use inhalation anesthetics.